1. Field of the Invention
This invention relates to endoscopes and is directed more particularly to an endoscope apparatus having means for conducting irrigation fluids to the distal end of the apparatus.
2. Description of the Prior Art
Endoscopes, which are instruments used to inspect cavities or openings, have found a great number of applications in medicine and other technologies. In the field of medicine, the use of endoscopes permits inspection of organs, or other biological specimens, for the purpose of inspecting a surgical site, sampling tissue, and/or facilitating the manipulation of other surgical instruments, usually with the objective of avoiding invasive and traumatizing surgical procedures.
Older conventional endoscopes used in medicine have an objective lens unit at their distal (forward) ends which transmits an image of the area forward of the objective lens unit to the proximal (rear) end of the endoscope for viewing in an eye-piece, the image being transmitted to the eye-piece via an image forwarding means in the form of a relay lens set or an optical fiber bundle unit. In more recent years, in place of the eye-piece and at least part of the image forwarding means, it has been preferred to provide a small size solid state video imaging device, such as one constituting a CCD chip, in the imaging plane of the objective lens, and applying the output of that video imaging device via a suitable electronic transmission system to a video monitor for viewing by a user. With both types of image transmitting and viewing arrangements, a surgeon can view the displayed image and use the information conveyed by that image to manipulate the endoscope and other surgical instruments that have been inserted into the patient via another incision or opening in the patient's body. In the case of endoscopes that incorporate a solid state video imaging device, the image seen by the objective lens unit can be observed in the display provided by the video monitor with or without magnification.
In U.S. patent application Ser. No. 08/319, 886, filed Oct. 7, 1994, now U.S. Pat. No. 5,582,576, in the names of Koichiro Hori, et al., there are shown and described optical, electronic and mechanical components of a contemporary endoscope.
It has been found to be beneficial to provide in or on endoscopes an irrigation tube for the purpose of providing fluid (liquid or gas, including air) to the distal end of the endoscope for (1) cleaning a window of the endoscope, and/or (2) irrigating an endoscopic site.
In the past, the need for irrigation has produced endoscope modifications not entirely successful. For example, some prior art devices have been provided with an external sheath around the outer surface of the endoscope, with the irrigant flowable between the endoscope and the surrounding sheath. However, a critical requirement of surgical endoscopes is that the maximum cross-sectional dimension of the endoscope be kept quite small, in keeping with the objective of avoiding invasive and traumatizing surgical procedures. The addition of an external sheath necessarily results in an increase in diameter of the endoscope.
In other prior art devices, a permanent external channel has been provided, which results in a local increase in diameter of the endoscope and, further, renders the endoscope difficult to use in conjunction with trocar sheaths of round cross-section.
In still other prior art devices, a small diameter irrigation tube has been integrated into the internal structure of the endoscope. The demands placed on the endoscope internal space necessitate very small irrigation tube diameters, which, because of their position and size, make sterilization of the irrigation tube very difficult.
Thus, in spite of previous attempts to solve the problem, there remains a need for an irrigation tube arrangement which requires little or no internal space, does not substantially enlarge the diameter of the endoscope, and is relatively easy to sterilize.